1. Field of the Invention
The invention relates to a chiral smectic liquid crystal device which is suitable for gradation display.
2. Related Background Art
With respect to a display apparatus using a ferroelectric chiral smectic liquid crystal, there is known a display apparatus in which a ferroelectric chiral smectic liquid crystal (hereinafter, referred to as an FLC) is injected into a liquid crystal cell which is constructed in a manner such that transparent electrodes are formed on two inner surfaces of glass substrates so as to keep a cell gap of about 1 to 3 .mu.m and are subjected to an orienting process and the resultant two glass substrates are arranged so as to face each other. Such display apparatuses have been disclosed in, for instance, U.S. Pat. Nos. 4639089, 4681404, 4682858, 4712873, 4712874, 4712875, 4712,877, 4714323, 4728176, 4738513, 4740060, 4765720, 4778259, 4796979, 4796980, 4859036, 4932757, 4932758, 5000545, and 5007716, and the like.
Among the above conventional techniques, particularly, in the case of a device in which a chevron structure shown in FIG. 1 is formed in the FLC and the FLC is oriented, a bright state under a cross nicols is excellent, so that an enough contrast is obtained. FIG. 1 shows a cross sectional view of the orientation state of an FLC arranged between substrates 11 and 12. An FLC 13 has a structure such that a layer 15 which is constructed by a plurality of liquid crystal molecules 14 is formed and a plurality of such layers 15 are arranged in the same direction and the layers 15 are bent. In the above case, it is preferable that the major axis of each of the liquid crystal molecules 14 is inclined from the substrates 11 and 12 at a pretilt angle .theta..sub.a of, preferably, 5.degree. or more. It is desirable that the above orientation state is obtained by performing the orienting process to the substrates 11 and 12 by rubbing processes 16 and 17 in the same direction.
As a gradation display method using the FLC, there are known methods disclosed in U.S. Pat. Nos. 4,655,561, 4,709,995, 4,712,877, 4,747,671, 4,763,994, 4,765,720, 4,776,676, 4,796,980, 4,802,744, 4,818,078, 4,824,218, and 4,938,574, and the like.